Coolant level is above specification
Check the coolant level. Refer to Procedure 008-018
External coolant leak
Inspect the engine for coolant leaking from hoses, drain cocks, water manifold, jumper tubes, expansion and pipe plugs, fittings, EGA cooler coolant supply and return tubes, EGA cooler vent lines, turbocharger coolant supply and return lines, EGA cooler, radiator core, air compressor and cylinder head gaskets, lubricating oil cooler, water pump seal, and OEM-mounted components that have coolant flow. If necessary, pressure-test the cooling system. Refer to Procedure 008-020.
Radiator cap is not correct, is malfunctioning, or has low-pressure rating
Check the radiator pressure cap. Refer to Procedure 008-020 and the OEM service manual.
Cooling system hose is collapsed, restricted, or leaking
Inspect the hoses. Refer to Procedure 008-020.
Fill line or vent lines are restricted, obstructed, or not routed correctly
Check the vent lines and the fill line for correct routing and for restriction. Refer to the OEM service manual.
Incorrect OEM plumbing routing, resulting in loss of coolant through the coolant overflow
Review plumbing to be positive that no high โข pressure coolant can cause backflow in the fill line. Refer to the OEM service manual.
Engine is overheating
Refer to the Coolant Temperature Above Normal Gradual Overheat symptom tree or the Coolant Temperature is Above Normal – Sudden Overheat symptom tree.
Air or combustion gases are entering the cooling system
Check for air or combustion gases in the cooling system. Refer to Procedure 008-020.